People who read books usually either interpose a bookmark between leaves of the book or fold back the leaf when interrupting reading and then closing the book, so that they can readily locate a page where they stopped reading. However, the now people who lead a busy life often read books for a chain of very short periods of time, such as, e.g., time of a commute to attend office or school, and its associated waiting time. In such a case, people sometimes forget to insert the bookmark between the pages of the book, and thus read the same page again when resuming reading. In order to obviate such an inconvenience, an automatic insertion bookmark has been proposed, in which when reading is interrupted, then a bookmark portion is automatically inserted between pages that were opened immediately before the book is closed.
One example of such an automatic insertion bookmark is proposed in, e.g., published Japanese Utility Model Application Laid-Open No. 6-83363. The bookmark as proposed in this publication includes a fixing plate, a band-like elastic plate, and a tongue piece. The fixing plate has an angular C shaped nick. The elastic plate extends sideward from one side of the fixing plate at an upper portion thereof. The tongue piece is disposed on the underside of the elastic plate at a distal end thereof. When the bookmark is used, the fixing plate is fixed to a book by means of the aforesaid nick, and then the tongue piece is laid on an opened page of the book. In this state, when the page is turned over, then the tongue piece is automatically placed on the following page. When the book is closed, then the tongue piece is held, as such, on the page. Thus, the tongue piece realizes a purpose of the automatic insertion bookmark.
However, in the automatically placed bookmark as proposed in the above publication, the rectangular-shaped fixing plate, bandlike elastic plate, and tongue piece are formed by a sheet, and are planar in their entirety. Accordingly, when a large number of pages are read and then turned over, it follows that many leaves of the book are present between the fixing plate and the tongue piece. As a result, the elastic plate is bent into a S-shape, and is then subjected to bending stress or torsional stress. This causes a problem that the tongue piece fails to reliably follow sequentially opened pages.
A further problem with the above bookmark is a poor appearance because the upper portion of the fixing plate and the entire surface of the elastic plate extend outward from the top of the book.
Another automatic insertion bookmark is proposed in published Japanese Patent Application Laid-Open No. 63-21192. The bookmark according to this publication includes fixing members and a string-like object. The fixing members are independent and separated from one another. The string-like object is made of a shrinkable raw material that has a proper length. The string-like object is suspendingly spanned between the fixing members. The fixing members are fixed to a cover of a book at respective positions that are spaced apart from a corner of the cover by respective small distances. The string-like object for connecting the fixing members together is spanned between the fixing members so as to extend across a corner portion of a predetermined page of the book.
However, the automatic insertion bookmark as proposed in the above publication has a problem that two fixing members must laboriously be fitted to the book. Further, the string-like object, which is made of a resilient member, must be fitted with some degree of tension. This brings about another problem that wrinkles in leaves of the book or the tendency of the leaves to bend would occur when the book is small in thickness because such tensioned string-like object pulls the corner portion of the book.